Circuit design and tubes The circuit uses a current input pair with A970 and C2240 in a double differential configuration, with A1145 and C2705 for voltage amplification to drive the power pair tube A1837 and C4793. The output stage uses the power pair tubes A1943 and C5200. Power supply Power supply is a dual supply with negative rails from 20V to 90V. The upgraded version optimizes the circuit and components. For direct voltage operation, it is recommended to stay below 90V and not push the voltage limit. Channel configuration The board is a singlechannel power amplifier board and requires a double channel setup for stereo use. Performance and capabilities With a supply of 20V to 90V and sufficient power, it can easily reach 200, delivering good sound quality, strong drive, and the ability to push a 15inch loudspeaker without strain. Use scenarios DIY home audio system requiring power to drive large speakers. Valve amplifier project or upgrade where tubebased amplification is desired. Small venue or stage monitoring setup needing robust, reliable amplification for capacity drivers.